This invention relates to an electronic musical instrument utilizing digital technique and more particularly an electronic musical instrument wherein musical tones are formed by repeatedly producing musical tone waveform elements.
In an electronic musical instrument, the tone pitch control of the generated musical tone and the tone generation control are performed by key informations which are generated in accordance with the key depressing operations of a keyboard unit; and waveform memory read out systems, harmonic wave synthesizing systems, etc., have been developed as the electronic musical instrument of the digital type.
In the electronic musical instrument of the waveform memory read out type, the musical tone waveform stored in the waveform memory device is repeatedly read out with a signal having a frequency corresponding to the tone pitch of a depressed key between an instant of generating a musical tone and the termination thereof, so that once the musical tone waveform to be stored in the waveform memory device is set, the tone color of the generated musical tone would be fixed with the result that it becomes impossible to vary at will the tone color. Thus, it is impossible to obtain a tone generation performance in which the tone color of the generated tone is varied delicately with time as in natural musical instruments.
Also in the conventional electronic musical instrument of the harmonic synthesizing type, a musical tone waveform which is set by a harmonic amplitude coefficient stored in a harmonic coefficient memory device is repeatedly generated by a signal having a frequency corresponding to the tone pitch of a depressed key between an instant of generating the musical tone and the termination thereof, so that, in the same manner as in the waveform memory read out system described above, once the harmonic amplitude coefficient to be stored in the harmonic coefficient memory device is set, it becomes impossible not only to vary the color of the generated tone but also to vary with time the color of the generated tone.
In the electronic musical instrument of the waveform memory read out system of the harmonic synthesizing system described above, for the purpose of varying the color of the generated musical tone or to vary with time the tone color, it has been proposed to provide a plurality of waveform memory devices for storing different musical tone waveforms or to provide a plurality of harmonic coefficient memory devices for storing a set of harmonic amplitude coefficients having different values and to select these waveform memory device groups or the harmonic coefficient memory device groups or to sequentially select them with time. However, these expedients require a plurality of memory devices (waveform memory devices or harmonic coefficient memory devices) and their transfer control devices thus complicating the construction and increasing the cost of the electronic musical instrument.